Step 1 — Make the Filling
Beat the softened cream cheese with an electric hand mixer until completely smooth — about 1 to 2 minutes. Add the powdered sweetener, cocoa powder, vanilla, and salt and beat until fully combined and uniform; it will look like thick chocolate frosting. Add the heavy cream and beat on high speed for 2 to 3 minutes until the mixture becomes noticeably lighter, fluffier, and mousse-like. It should hold soft peaks. Do not overbeat.
Step 2 — Chill Until Firm
Line a 9x5-inch loaf pan with parchment paper, leaving overhang on the long sides for easy lifting. Transfer the filling to the pan, spread into an even layer, and smooth the top flat. Cover loosely and refrigerate for at least 3 hours until firm enough to cut cleanly — overnight produces the best results. To speed things up, freeze for 1 to 1.5 hours instead, until firm but not rock-solid.
